Special railroad cars are used to transport vehicles such as automobiles and trucks from manufacturing plants to distribution centers. Such railroad cars are often referred to as auto rack cars. The number of decks which support the vehicles depends on the type of vehicles to be transported. Although some cars have a single deck it is more common to have two or three decks. Each deck will usually carry about four to six vehicles in the United States.
It is necessary to tie down or secure each vehicle to its supporting deck so that it remains in position while the railroad car moves from its point of loading to its destination. The system used to tie down each vehicle must be able to hold it securely even when the railroad car is subjected to buff and draft forces as well as when it rocks, rolls and bumps.
One of the ways widely used in the United States to tie down vehicles requires a pair of parallel tracks, spaced apart about forty inches outside, on each deck. The four wheels of each vehicle span the tracks and thus provide centering guides when the vehicles are driven onto the railroad car in column formation in so-called circus loading. After a vehicle is properly positioned on a deck it is pulled down tightly by use of four chains. Two chains are used at each end. Each chain free end is hooked to the vehicle frame or body adjacent the track. The chain extends downwardly to a carriage releasably slidable in the track and carrying a winch for tightening the chain. Such apparatus is disclosed in the U.S. Pat. Nos. 3,566,803; 3,564,577; 3,374,008 and 3,673,969.
Although the described tie down apparatus has been successfully used for many years, recent vehicle structural changes have lowered road clearance, indicating that alternative systems should be used. Thus, it is no longer desirable to use a tie down system which pulls the body down and compresses the vehicle springs because this lowers the clearance between the vehicle underbody parts including mufflers, tailpipes and the like, and the deck. When the railroad car bumps and pitches, it can hit the deck and cause damage to the vehicle. Also important is the fact that such tie down systems introduce point loads into the underframe, which is very undesirable. Additionally, to withstand the tension applied to the underbody of the vehicle where the hooks are attached, special reinforcement must be added with increased cost solely to transport the vehicle and with no general benefit to the vehicle once it reaches its destination.
A further disadvantage of the prior art tie down system is that the laborer must have access to both sides of the vehicle; thus, space must be provided for him to work and walk on both sides. For some vehicles it is considered that tie down on one side only would be adequate if a suitable system is available. This would reduce the laborers time and lower costs.
Although the above discussion has pertained specifically to transporting vehicles on railroad cars, it is also common to transport vehicles on over-the-highway trailers and trucks, on ships, barges and boats, by air cargo planes, and in shipping containers. As to shipping containers, automobiles are very often shipped in them by railroad and ship. Thus, servicemen, such as Army and Navy personnel being transferred to and from a base overseas, take their automobiles along and in such cases the automobiles are often transported in containers. When a vehicle is shipped in a container or by trailer, truck, ship, barge, boat or air cargo plane, it is often desirable, and many times necessary, to have a tie down apparatus secure the vehicle in place.
During the last few years several United States patents have been granted for chock blocks which avoid use of a tie-down mechanism which requires attachment to the vehicle chassis, frame or axle. Thus, U.S. Pat. Nos. 4,688,140; 4,674,929 and 4,679,974 disclose chock blocks which are placed beneath one or more tires to secure the vehicle in place. These chock blocks are secured to one or more tracks, secured to a supporting deck, located along the outside of the vehicle wheels. An optional tie-down strap can extend over the tire and be connected to a chock block adjacent to, and fore and aft of, the tire tread. This permits the vehicle suspension to absorb vertical shocks whereas previous systems which tied to the chassis only permitted the tires to absorb vertical shocks.
A chock block of the general type just described which has found substantial commercial acceptance is marketed by Thrall Car Manufacturing Company under the name Wedge Chock. The chock block is disclosed in copending patent application Ser. No. 165,845 filed Mar. 9, 1988, the entire contents of which is incorporated herein by reference. The chock block disclosed in that application is asymmetrical and the chock blocks positioned against opposing portions of a tire tread are mirror images of each other. This requires the manufacture of two separate chock blocks with each one having a locking pin, which engages a hole in the track, positioned on each chock block away from the tire tread so that it is accessible for manual operation. They cannot be interchanged because that would position the locking pin handle adjacent the tire tread and make it inaccessible. A need accordingly exists for a chock block which is symmetrical, so that only one form need be manufactured and one form inventoried by the user, which is usable fore and aft of a tire tread and which has a manual locking mechanism which can be observed and operated from either of said positions while the chock block presses against the tire tread and is locked or secured to the track.